Method for transmitting and receiving random access preamble in wireless communication system and device therefor

ABSTRACT

Provided is a method for transmitting a random access preamble by a user equipment (UE) in a wireless communication system supporting a narrow band-Internet of things (NB-IoT). Specifically, the UE transmits the random access preamble to an eNB in a subcarrier allocated by the eNB according to a specific preamble structure and receives a random access response message from the eNB in response to the random access preamble. In this case, the random access preamble is repeatedly transmitted 16 times during a predetermined duration and then, a gap is inserted for a predetermined time and the predetermined duration is determined by multiplying a transmission duration in which the random access preamble is transmitted by the number of repeated transmission times.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/669,979, filed on May 10, 2018, the entire contents of which arehereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a method for transmitting and receivinga random access preamble in a wireless communication system, and moreparticularly, to a method for transmitting and receiving a random accesspreamble in a wireless communication system supportingNarrowBand-Internet of Things (NB-IoT) and a device for supporting thesame.

Related Art

Mobile communication systems have been generally developed to providevoice services while guaranteeing user mobility. Such mobilecommunication systems have gradually expanded their coverage from voiceservices through data services up to high-speed data services. However,as current mobile communication systems suffer resource shortages andusers demand even higher-speed services, development of more advancedmobile communication systems is needed.

The requirements of the next-generation mobile communication system mayinclude supporting huge data traffic, a remarkable increase in thetransfer rate of each user, the accommodation of a significantlyincreased number of connection devices, very low end-to-end latency, andhigh energy efficiency. To this end, various techniques, such as smallcell enhancement, dual connectivity, massive multiple input multipleoutput (MIMO), in-band full duplex, non-orthogonal multiple access(NOMA), supporting super-wideband, and device networking, have beenresearched.

SUMMARY OF THE INVENTION

The present invention provides a method for transmitting and receiving arandom access preamble in a wireless communication system supportingNarrowBand-Internet of Things (NB-IoT).

The present invention also provides a structure of a physical randomaccess channel (PRACH) for cell range extension.

The present invention also provides a method for preventing performancedeterioration and synchronization deviation which may occur due torepetitive transmission of a random access preamble.

The technical objects of the present invention are not limited to theaforementioned technical objects, and other technical objects, which arenot mentioned above, will be apparently appreciated by a person havingordinary skill in the art from the following description.

In an aspect, provided is a method for transmitting a random accesspreamble by a user equipment (UE) in a wireless communication systemsupporting a narrow band-Internet of things (NB-IoT), which includes:transmitting, to a base station, a random access preamble according to aspecific preamble structure in a subcarrier allocated by the basestation; and receiving, from the base station, a random access responsemessage in response to the random access preamble, in which a gap isinserted for a predetermined time after the random access preamble isrepeatedly transmitted 16 times during a predetermined duration, and thepredetermined duration is determined by multiplying a transmissionduration transmitted by the random access preamble by the number ofrepeated transmission times of the random access preamble.

Furthermore, in the present invention, the transmission duration isconstituted by a symbol group of a Cyclic Prefix (CP) and three symbolsaccording to the specific preamble structure.

Furthermore, in the present invention, a subcarrier of the symbol groupis hopped on a frequency axis in a specific pattern constituted by ahopping pair symmetric according to the specific preamble structure.

Furthermore, in the present invention, subcarrier indexes of second andthird symbol groups are values larger than a subcarrier index of aprevious symbol group by ‘1’ or smaller than the subcarrier index by ‘1’based on a start symbol group of the specific pattern, subcarrierindexes of the third symbol group and a fourth symbol group are valueslarger than the subcarrier index by ‘3’ or smaller than the subcarrierindex ‘3’, and a subcarrier index of a fifth symbol group is a valuelarger than the subcarrier index of the previous symbol group by ‘18’.

Furthermore, in the present invention, a subcarrier spacing is 1.25 kHzin the specific preamble structure.

Furthermore, in the present invention, the gap is ‘40’ ms.

Furthermore, in the present invention, the random access responsemessage includes a timing advance command value for adjusting uplinktransmission timing of the UE.

Furthermore, in the present invention, the method further includesperforming uplink transmission based on the timing advance commandvalue.

Furthermore, in the present invention, provided is a method forreceiving a random access preamble by a base station in a wirelesscommunication system supporting a narrow band-Internet of things(NB-IoT), which includes: receiving, from a UE, a random access preambleaccording to a specific preamble structure in an allocated subcarrier;and transmitting, to the UE, a random access response message inresponse to the random access preamble, in which wherein a gap isinserted for a predetermined time after the random access preamble isrepeatedly transmitted 16 times during a predetermined duration, and thepredetermined duration is determined by multiplying a transmissionduration transmitted by the random access preamble by the number ofrepeated transmission times of the random access preamble.

Furthermore, in the present invention, provided is a UE transmitting arandom access preamble in a wireless communication system supporting anarrow band-Internet of things (NB-IoT), which includes: a radiofrequency (RF) module for transmitting and receiving a radio signal; anda processor functionally connected with the RF module, in which theprocessor is configured to transmit, to a base station, a random accesspreamble according to a specific preamble structure in a subcarrierallocated by the base station, and receive, from the base station, arandom access response message in response to the random accesspreamble, and a gap is inserted for a predetermined time after therandom access preamble is repeatedly transmitted 16 times during apredetermined duration, and the predetermined duration is determined bymultiplying a transmission duration transmitted by the random accesspreamble by the number of repeated transmission times of the randomaccess preamble.

This specification has an effect that a cell range may be extended bytransmitting a random access preamble through a structure of a newphysical random access channel (PRACH).

This specification also has an effect that performance deterioration andsynchronization deviation may be prevented by transmitting repeatedlytransmitting a random access preamble a specific number of times at thetime of repeatedly transmitting the random access preamble and then,inserting a gap for stopping transmission for a predetermined time.

Advantages which can be obtained in the present invention are notlimited to the aforementioned effects and other unmentioned advantageswill be clearly understood by those skilled in the art from thefollowing description.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to help understanding of the present invention, theaccompanying drawings which are included as a part of the DetailedDescription provide embodiments of the present invention and describethe technical features of the present invention together with theDetailed Description.

FIG. 1 is a diagram illustrating an example of an overall systemstructure of NR to which a method proposed in the present specificationmay be applied.

FIG. 2 illustrates a relationship between an uplink frame and a downlinkframe in a wireless communication system to which the method proposed inthe present specification may be applied.

FIG. 3 illustrates an example of a resource grid supported in thewireless communication system to which the method proposed in thepresent specification may be applied.

FIG. 4 shows examples of antenna ports and resource grids for eachnumerology to which a method proposed in this specification may beapplied.

FIG. 5 is a diagram showing an example of a self-contained slotstructure to which a method proposed in this specification may beapplied.

FIGS. 6 and 7 are diagrams illustrating an example of a hopping intervalof a preamble in a wireless communication system to which a methodproposed in this specification may be applied.

FIGS. 8A and 8B illustrate an example of a symbol group for a randomaccess in a wireless communication system to which a method proposed inthis specification may be applied.

FIGS. 9A and 9B are diagrams illustrating an example of a frequencyhopping method of a random access preamble proposed in thisspecification.

FIG. 10 is a diagram illustrating another example of a frequency hoppingmethod of a random access preamble proposed in this specification.

FIG. 11 is a diagram illustrating yet another example of a frequencyhopping method of a random access preamble proposed in thisspecification.

FIGS. 12A and 12B are diagrams illustrating still yet another example ofa frequency hopping method of a random access preamble proposed in thisspecification.

FIG. 13 is a diagram illustrating an example of a time gap configuringmethod of a random access preamble proposed in this specification.

FIG. 14 is a flowchart illustrating an example of an operation method ofa UE that performs a method proposed in this specification.

FIG. 15 is a flowchart illustrating an example of an operation method ofan eNB that performs a method proposed in this specification.

FIG. 16 illustrates a block diagram of a wireless communication deviceto which methods proposed in this specification may be applied.

FIG. 17 illustrates another example of the block diagram of the wirelesscommunication device to which the methods proposed in this specificationmay be applied.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Some embodiments of the present disclosure are described in detail withreference to the accompanying drawings. A detailed description to bedisclosed along with the accompanying drawings is intended to describesome exemplary embodiments of the present disclosure and is not intendedto describe a sole embodiment of the present disclosure. The followingdetailed description includes more details in order to provide fullunderstanding of the present disclosure. However, those skilled in theart will understand that the present disclosure may be implementedwithout such more details.

In some cases, in order to avoid making the concept of the presentdisclosure vague, known structures and devices are omitted or may beshown in a block diagram form based on the core functions of eachstructure and device.

In the present disclosure, a base station has the meaning of a terminalnode of a network over which the base station directly communicates witha terminal. In this document, a specific operation that is described tobe performed by a base station may be performed by an upper node of thebase station according to circumstances. That is, it is evident that ina network including a plurality of network nodes including a basestation, various operations performed for communication with a terminalmay be performed by the base station or other network nodes other thanthe base station. The base station (BS) may be substituted with anotherterm, such as a fixed station, a Node B, an eNB (evolved-NodeB), a basetransceiver system (BTS), or an access point (AP) gNB (next generationNB, general NB, gNodeB). Furthermore, the terminal may be fixed or mayhave mobility and may be substituted with another term, such as userequipment (UE), a mobile station (MS), a user terminal (UT), a mobilesubscriber station (MSS), a subscriber station (SS), an advanced mobilestation (AMS), a wireless terminal (WT), a machine-type communication(MTC) device, a machine-to-Machine (M2M) device, or a device-to-device(D2D) device.

Hereinafter, downlink (DL) means communication from a base station toUE, and uplink (UL) means communication from UE to a base station. InDL, a transmitter may be part of a base station, and a receiver may bepart of UE. In UL, a transmitter may be part of UE, and a receiver maybe part of a base station.

Specific terms used in the following description have been provided tohelp understanding of the present disclosure, and the use of suchspecific terms may be changed in various forms without departing fromthe technical sprit of the present disclosure.

The following technologies may be used in a variety of wirelesscommunication systems, such as code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), and non-orthogonalmultiple access (NOMA). CDMA may be implemented using a radiotechnology, such as universal terrestrial radio access (UTRA) orCDMA2000. TDMA may be implemented using a radio technology, such asglobal system for mobile communications (GSM)/general packet radioservice (GPRS)/enhanced data rates for GSM evolution (EDGE). OFDMA maybe implemented using a radio technology, such as Institute of electricaland electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX),IEEE 802.20, or evolved UTRA (E-UTRA). UTRA is part of a universalmobile telecommunications system (UMTS). 3rd generation partnershipproject (3GPP) Long term evolution (LTE) is part of an evolved UMTS(E-UMTS) using evolved UMTS terrestrial radio access (E-UTRA), and itadopts OFDMA in downlink and adopts SC-FDMA in uplink. LTE-advanced(LTE-A) is the evolution of 3GPP LTE.

Further, 5G new radio (NR) defines Enhanced Mobile Broadband (eMBB),Massive Machine Type Communications (mMTC), Ultra-Reliable and LowLatency Communications (URLLC), and vehicle-to-everything (V2X)according to a usage scenario.

In addition, the 5G NR standard is divided into standalone (SA) andnon-standalone (NSA) depending on co-existence between the NR system andthe LTE system.

In addition, the 5G NR supports various subcarrier spacings, andsupports CP-OFDM in the downlink and CF-OFDM and DFT-s-OFDM (SC-OFDM) inthe uplink.

Three major requirement areas of 5G include (1) an Enhanced MobileBroadband (eMBB) area, (2) a Massive Machine Type Communication (mMTC)area, and (3) an Ultra-reliable and Low Latency Communications (URLLC)area.

Some use cases may require multiple areas for optimization and other usecases may only focus on only one key performance indicator (KPI). 5G isto support the various use cases in a flexible and reliable method.

eMBB far surpasses basic mobile Internet access and covers media andentertainment applications in rich interactive work, cloud or augmentedreality. Data is one of the key drivers of 5G and may not be able to seededicated voice services for the first time in the 5G era. In 5G; thevoice is expected to be processed as an application program simply byusing data connection provided by a communication system. Main reasonsfor an increased traffic volume are an increase in content size and anincrease in number of applications requiring a high data rate. Astreaming service (audio and video), an interactive video, and mobileInternet connection will be more widely used as more devices areconnected to the Internet. A lot of application programs requirealways-on connectivity in order to push real-time information andnotification to a user. Cloud storages and applications are growingrapidly in mobile communication platforms, which may be applied to bothwork and entertainment. In addition, the cloud storage is a special usecase of drives a growth of an uplink data transmission rate. 5G is alsoused in remote work of the cloud and requires a lower end-to-end latencyso as to maintain an excellent user experience when a tactile interfaceis used. The entertainment, for example, a cloud game and videostreaming are another key factor for increasing a demand for a mobilebroadband capability. The entertainment is required in a smart phone anda tablet anywhere including a high mobility environment such as a train,a vehicle, and an airplane. Another use case is augmented reality andinformation retrieval for the entertainment. Here, the augmented realityrequires a very low latency and an instantaneous data amount.

Further, one of 5G use cases most expected relates to a function tosmoothly connect an embedded sensor in all fields, that is, mMTC. By2020, the number of potential IoT devices is expected to reach 20.4billion. Industry IoT is one of the areas where 5G plays a key role inenabling smart cities, asset tracking, smart utilities, agriculture, andsecurity infrastructures.

URLLC includes new services that will change the industry through ultrareliable/usable links with low latency such as remote control of keyinfrastructure and self-driving vehicles. Levels of reliability andlatency are required for smart grid control, industrial automation,robotics, and drone control and adjustment.

Next, multiple use cases will be described in more detail.

5G may complement fiber-to-the-home (FTTH) and cable-based broadband (orDOCSIS) as a means of providing streams rated at gigabits per second athundreds of megabits per second. Such a fast speed is required todeliver TVs with resolutions of 4K and above (6K, 8K, and above) as wellas virtual reality and the augmented reality. The Virtual Reality (VR)and Augmented Reality (AR) applications include mostly immersive sportsgames. A specific application program may require a special networkconfiguration. For example, in the case of a VR game, game companies mayneed to integrate a core server with an edge network server of a networkoperator in order to minimize latency.

Automotive is expected to become an important new power for 5G with manyuse cases for mobile communications to vehicles. For example,entertainment for passengers demands simultaneous high capacity and highmobility mobile broadband. The reason is that future users will continueto expect high-quality connections regardless of locations and speedsthereof. Another utilization examples of an automotive field is anaugmented-reality dashboard. This identifies an object in the dark overwhat a driver is seeing through a front window, and overlaps anddisplays information that tells the driver regarding a distance and amotion of the object. In the future, a wireless module enablescommunication between vehicles, information exchange between the vehicleand a supported infrastructure, and information exchange between thevehicle and other connected devices (e.g., devices carried by apedestrian). A safety system guides an alternative course of an actionin order for the driver to drive safer driving, thereby reducing therisk of accidents. A next step will be a remotely controlled orself-driven vehicle. This requires very reliable and very fastcommunication between different self-driving vehicles and between theautomatic and the infrastructure. In the future, the self-driven vehiclewill perform all driving activities and the driver will focus only ontraffic which the vehicle itself may not identify. Technicalrequirements of the self-driven vehicle require ultra-low latency andultra-high-speed reliability so as to increase a traffic safety to alevel not achievable by humans.

Smart cities and smart homes, referred to as smart societies, will beembedded into high-density wireless sensor networks. A distributednetwork of intelligent sensors will identify conditions for cost andenergy-efficient maintenance of a city or house. A similar configurationmay be performed for each home. Temperature sensors, windows and heatingcontrollers, burglar alarms, and appliances are all wirelesslyconnected. Many of the sensors typically have low data rate, low power,and low cost. However, for example, real-time HD video may be requiredfor specific types of devices for monitoring.

Consumption and distribution of energy including heat or gas is highlydispersed, requiring automated control of distributed sensor networks. Asmart grid interconnects the sensors using digital information andcommunication technologies to collect information and act based on theinformation. The information may include vendor and consumer behaviors,allowing the smart grid to improve the distribution of fuels, such aselectricity, in an efficiency, reliability, economics, andsustainability of production and in an automated way. The smart grid maybe regarded as another sensor network with low latency.

A health sector has many application programs that may benefit frommobile communications. Communication systems may support telemedicine toprovide clinical care in remote locations. This may help to reducebarriers to a distance and improve an access to health services that arenot continuously available in distant rural areas. This is also used tosave lives in critical care and emergency situations. Wirelesscommunication based wireless sensor networks may provide remotemonitoring and sensors for parameters such as heart rate and bloodpressure.

Wireless and mobile communications are becoming increasingly importantin industrial application fields. Wires are high in installation andmaintenance cost. Thus, a possibility of replacing cables withreconfigurable wireless links is an attractive opportunity in manyindustries. However, achieving this requires that wireless connectionsoperate with similar delay, reliability, and capacity as cables, andthat their management is simplified. Low latency and very low errorprobabilities are new requirements that need to be connected to 5G.

Logistics and freight tracking are important use cases of mobilecommunications that enable tracking of inventory and packages anywhereusing location based information systems. Use cases of logistics andfreight tracking typically require low data rates, but require a largerange and reliable location information.

Embodiments of the present disclosure may be supported by the standarddocuments disclosed in at least one of IEEE 802, 3GPP, and 3GPP2, thatis, radio access systems. That is, steps or portions that belong to theembodiments of the present disclosure and that are not described inorder to clearly expose the technical spirit of the present disclosuremay be supported by the documents. Furthermore, all terms disclosed inthis document may be described by the standard documents.

In order to more clarify a description, 3GPP LTE/LTE-A/NR (New RAT) ischiefly described, but the technical characteristics of the presentdisclosure are not limited thereto.

Definition of Terms

eLTE eNB: An eLTE eNB is an evolution of an eNB that supports aconnection for an EPC and an NGC.

gNB: A node for supporting NR in addition to a connection with an NGC

New RAN: A radio access network that supports NR or E-UTRA or interactswith an NGC

Network slice: A network slice is a network defined by an operator so asto provide a solution optimized for a specific market scenario thatrequires a specific requirement together with an inter-terminal range.

Network function: A network function is a logical node in a networkinfra that has a well-defined external interface and a well-definedfunctional operation.

NG-C: A control plane interface used for NG2 reference point between newRAN and an NGC

NG-U: A user plane interface used for NG3 reference point between newRAN and an NGC

Non-standalone NR: A deployment configuration in which a gNB requires anLTE eNB as an anchor for a control plane connection to an EPC orrequires an eLTE eNB as an anchor for a control plane connection to anNGC

Non-standalone E-UTRA: A deployment configuration an eLTE eNB requires agNB as an anchor for a control plane connection to an NGC.

User plane gateway: A terminal point of NG-U interface

Numerology: Corresponds to one subcarrier spacing in a frequency domain.Different numerology may be defined by scaling reference subcarrierspacing to an integer N.

NR: NR Radio Access or New Radio

General System

FIG. 1 is a diagram illustrating an example of an overall structure of anew radio (NR) system to which a method proposed by the presentdisclosure may be implemented.

Referring to FIG. 1, an NG-RAN is composed of gNBs that provide an NG-RAuser plane (new AS sublayer/PDCP/RLC/MAC/PHY) and a control plane (RRC)protocol terminal for a UE (User Equipment).

The gNBs are connected to each other via an Xn interface.

The gNBs are also connected to an NGC via an NG interface.

More specifically, the gNBs are connected to a Access and MobilityManagement Function (AMF) via an N2 interface and a User Plane Function(UPF) via an N3 interface.

New Rat (NR) Numerology and Frame Structure

In the NR system, multiple numerologies may be supported. Thenumerologies may be defined by subcarrier spacing and a CP (CyclicPrefix) overhead. Spacing between the plurality of subcarriers may bederived by scaling basic subcarrier spacing into an integer N (or^(μ)).In addition, although a very low subcarrier spacing is assumed not to beused at a very high subcarrier frequency, a numerology to be used may beselected regardless of a frequency band.

In addition, in the NR system, a variety of frame structures accordingto the multiple numerologies may be supported.

Hereinafter, an Orthogonal Frequency Division Multiplexing (OFDM)numerology and a frame structure, which may be considered in the NRsystem, will be described.

A plurality of OFDM numerologies supported in the NR system may bedefined as in Table 1.

TABLE 1 μ Δf = 2^(μ) · 15 [kHz] Cyclic prefix 0 15 Normal 1 30 Normal 260 Normal, Extended 3 120 Normal 4 240 Normal 5 480 Normal

Regarding a frame structure in the NR system, a size of various fieldsin the time domain is expressed as a multiple of a time unit ofT_(s)=1/(Δf_(max)·N_(f)). In this case, Δf_(max)=480·10³, andN_(f)=4096. DL and UL transmission is configured as a radio frame havinga section of T_(f)=(Δf_(max)N_(f)/100)·T_(s)=10 ms. The radio frame iscomposed of ten subframes each having a section ofT_(sf)=(Δf_(max)=N_(f)/1000)·T_(s)=1 ms. In this case, there may be aset of UL frames and a set of DL frames.

FIG. 2 illustrates a relationship between a UL frame and a DL frame in awireless communication system to which a method proposed by the presentdisclosure may be implemented.

As illustrated in FIG. 2, a UL frame number I from a User Equipment (UE)needs to be transmitted T_(TA)=N_(TA)T_(s) before the start of acorresponding DL frame in the UE.

Regarding the numerology μ, slots are numbered in ascending order ofn_(s) ^(μ)∈{0, . . . , N_(subframe) ^(slots, μ)−1} in a subframe, and inascending order of n_(s,f) ^(μ)∈{0, . . . , N_(frame) ^(slots,μ)−1} in aradio frame. One slot is composed of continuous OFDM symbols of N_(symb)^(μ), and N_(symb) ^(μ) is determined depending on a numerology in useand slot configuration. The start of slots n_(s) ^(μ) in a subframe istemporally aligned with the start of OFDM symbols n_(s) ^(μ)N_(symb)^(μ) in the same subframe.

Not all UEs are able to transmit and receive at the same time, and thismeans that not all OFDM symbols in a DL slot or an UL slot are availableto be used.

Table 2 shows the number of OFDM symbols per slot for a normal CP in thenumerology μ, and Table 3 shows the number of OFDM symbols per slot foran extended CP in the numerology μ.

TABLE 2 Slot configuration 0 1 μ N_(symb) ^(μ) N_(frame) ^(slots,μ)N_(subframe) ^(slots,μ) N_(symb) ^(μ) N_(frame) ^(slots,μ) N_(subframe)^(slots,μ) 0 14 10 1 7 20 2 1 14 20 2 7 40 4 2 14 40 4 7 80 8 3 14 80 8— — — 4 14 160 16 — — — 5 14 320 32 — — —

TABLE 3 Slot configuration 0 1 μ N_(symb) ^(μ) N_(frame) ^(slots,μ)N_(subframe) ^(slots,μ) N_(symb) ^(μ) N_(frame) ^(slots,μ) N_(subframe)^(slots,μ) 0 12 10 1 6 20 2 1 12 20 2 6 40 4 2 12 40 4 6 80 8 3 12 80 8— — — 4 12 160 16 — — — 5 12 320 32 — — —

NR Physical Resource

Regarding physical resources in the NR system, an antenna port, aresource grid, a resource element, a resource block, a carrier part,etc. may be considered.

Hereinafter, the above physical resources possible to be considered inthe NR system will be described in more detail.

First, regarding an antenna port, the antenna port is defined such thata channel over which a symbol on one antenna port is transmitted can beinferred from another channel over which a symbol on the same antennaport is transmitted. When large-scale properties of a channel receivedover which a symbol on one antenna port can be inferred from anotherchannel over which a symbol on another antenna port is transmitted, thetwo antenna ports may be in a QC/QCL (quasi co-located or quasico-location) relationship. Herein, the large-scale properties mayinclude at least one of delay spread, Doppler spread, Doppler shift,average gain, and average delay.

FIG. 3 shows an example of a resource grid supported in a wirelesscommunication system to which a method proposed in this specificationmay be applied.

FIG. 3 illustrates an example in which a resource grid includes N_(RB)^(μ)N_(sc) ^(RB) subcarriers on the frequency domain and one subframeincludes 14·2μ OFDM symbols, but the present invention is not limitedthereto.

In the NR system, a transmitted signal is described by one or moreresource grids including N_(RB) ^(μ)N_(sc) ^(RB) subcarriers and2^(μ)N_(symb) ^((μ)) OFDM symbols. In this case, N_(RB) ^(μ)≤N_(RB)^(max, μ). The N_(RB) ^(max,μ) indicates a maximum transmissionbandwidth, which may be different between numerologies and betweenuplink and downlink.

In this case, as in FIG. 4, one resource grid may be configured for eachnumerology μ and antenna port p.

FIG. 4 shows examples of antenna ports and resource grids for eachnumerology to which a method proposed in this specification may beapplied.

Each element of the resource grid for the numerology μ and the antennaport p is indicated as a resource element, and may be uniquelyidentified by an index pair (k,l). Herein, k=0, . . . , N_(RB)^(μ)N_(sc) ^(RB)−1 is an index in the frequency domain, and l=0, . . .2^(μ)N_(symb) ^((μ))−1 indicates a location of a symbol in a subframe.To indicate a resource element in a slot, the index pair (k,l) is used.Herein, l=0, . . . , N_(symb) ^(μ)−1.

The resource element (k,l) for the numerology μ and the antenna port pcorresponds to a complex value a_(k,l) ^((p,μ)). When there is no riskof confusion or when a specific antenna port or numerology is specified,the indexes p and μ may be dropped and thereby the complex value maybecome a_(k,l) ^((p)) or a_(k,l) .

In addition, a physical resource block is defined as N_(sc) ^(RB)=12continuous subcarriers in the frequency domain. In the frequency domain,physical resource blocks may be numbered from 0 to N_(RB) ^(μ)−1. Atthis point, a relationship between the physical resource block numbern_(PRB) and the resource elements (k,l) may be given as in Equation 1

$\begin{matrix}{n_{PRB} = \lfloor \frac{k}{N_{sc}^{RB}} \rfloor} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack\end{matrix}$

In addition, regarding a carrier part, a UE may be configured to receiveor transmit the carrier part using only a subset of a resource grid. Atthis point, a set of resource blocks which the UE is configured toreceive or transmit are numbered from 0 to N_(URB) ^(μ)−1 in thefrequency region.

Self-Contained Slot Structure

In order to minimize latency of data transmission in the TDD system, aself-contained slot structure, such as FIG. 5, is taken intoconsideration in a 5-generation New RAT (NR).

That is, FIG. 5 is a diagram showing an example of a self-contained slotstructure to which a method proposed in this specification may beapplied.

In FIG. 5, a slashed region 510 indicates a downlink control region, anda black part 520 indicates an uplink control region.

A part 530 having no indication may be used for downlink datatransmission and may be used for uplink data transmission.

The characteristics of such a structure is that DL transmission and ULtransmission are sequentially performed within one slot and DL data istransmitted and UL Ack/Nack may also be transmitted and received withinone slot.

Such a slot may be defined as a “self-contained slot.”

That is, through such a slot structure, a base station can reduce thetime taken for data retransmission to a UE when a data transmissionerror occurs, thereby being capable of minimizing latency of the finaldata delivery.

In such a self-contained slot structure, a base station and a UE requirea time gap for a process from a transmission mode to a reception mode ora process from the reception mode to the transmission mode.

To this end, in the corresponding slot structure, some OFDM symbols atan instance from DL to UL is configured as a guard period (GP).

Latency for Infrequent Small Packets

For infrequent application layer small packet/message transfer, the timeit takes to successfully deliver an application layer packet/messagefrom the radio protocol layer 2/3 SDU ingress point at the mobile deviceto the radio protocol layer 2/3 SDU egress point in the RAN, when themobile device starts from its most “battery efficient” state.

For the definition above, the latency shall be no worse than 10 secondson the uplink for a 20 byte application packet (with uncompressed IPheader corresponding to 105 bytes physical layer) measured at themaximum coupling loss (MaxCL) of 164 dB.

Analytical evaluation is the baseline evaluation methodology and systemlevel evaluation can be considered if needed.

Coverage

MaxCL in uplink and downlink between device and Base Station site(antenna connector(s)) for a data rate of 160 bps, where the data rateis observed at the egress/ingress point of the radio protocol stack inuplink and downlink.

The target for coverage should be 164 dB and link budget and/or linklevel analysis are used as the evaluation methodology.

Extreme Coverage

The coupling loss is defined as the total long-term channel loss overthe link between the UE antenna ports and the eNode B antenna ports, andincludes in practice antenna gains, path loss, shadowing, body loss,etc.

The MaxCL is the limit value of the coupling loss at which the servicecan be delivered, and therefore defines the coverage of the service andthe MaxCL is independent of the carrier frequency. In this case, theMaxCL is defined in the UL and DL in Equation 2 below:

UL MaxCL=UL Max Tx power−eNB Sensitivity

DL MaxCL=DL Max Tx power−UE Sensitivity  [Equation 2]

The MaxCL is evaluated via link budget analysis (supported by link levelsimulations) and the proposed MaxCL calculation template is given inTable 4 below.

TABLE 4 Item Value Transmitter (1) Tx power (dBm) Receiver (2) Thermalnoise density (dBm/Hz) (3) Receiver noise figure (dB) (4) Interferencemargin (dB) (5) Occupied channel bandwidth (Hz) (6) Effective noisepower = (2) + (3) + (4) + 10 log(5) (dBm) (7) Required SINR (dB) (8)Receiver sensitivity = (6) + (7) (dBm) (9) MaxCL = (1) − (8) (dB)

In this case, an assumption shown in Table 5 below may be used.

TABLE 5 UE Tx power 23 dBm DL Tx power 46 dBm eNB receiver noise figure 5 dB UE receiver noise figure  9 dB Interference margin  0 dB

For a basic MBB service characterized by a downlink data rate of 2 Mbpsand an uplink data rate of 60 kbps for stationary users, the target onmaximum coupling loss is 140 dB and for mobile users a downlink datarate of 384 kbps is acceptable.

For a basic MBB service characterized by a downlink data rate of 1 Mbpsand an uplink data rate of 30 kbps for stationary users, the target onmaximum coupling loss is 143 dB. At this coupling loss relevant downlinkand uplink control channels should also perform adequately.

As the evaluation methodology, link budget and/or link level analysisare used for extreme long distance coverage in low density areas.

UE Battery Life

UE battery life can be evaluated by the battery life of the UE withoutrecharge. For mMTC, UE battery life in extreme coverage shall be basedon the activity of mobile originated data transfer consisting of 200bytes UL per day followed by 20 bytes DL from MaxCL of 164 dB, assuminga stored energy capacity of 5 Wh.

The target for UE battery life for mMTC should be beyond 10 years, 15years is desirable.

Analytical evaluation is used as the evaluation methodology.

Connection Density

Connection density refers to total number of devices fulfilling a targetQoS per unit area (per km2). The target QoS is to ensure a system packetdrop rate less than 1% under given packet arrival rate 1 and packet sizeS. Packet drop rate=(Number of packet in outage)/(number of generatedpackets), where a packet is in outage if this packet failed to besuccessfully received by destination receiver beyond packet droppingtimer.

The target for connection density should be 1000000 device/km² in anurban environment.

3GPP should develop standards with means of high connection efficiency(measured as supported number of devices per TRxP per unit frequencyresource) to achieve the desired connection density and analytical, linklevel evaluation and system level evaluation are to be performed forUrban coverage for massive connection (urban environment).

LTE PRACH

Table 6 below illustrates an example of a PRACH format supported in LTE.

TABLE 6 Preamble CP duration GT duration Max. delay Max. cell format(us) (us) spread (us) radius (km) 0 103.1 96.88 6.3 14.5 1 684.4 515.616.7 77.3 2 203.1 196.9 6.3 29.5 3 684.4 715.6 16.7 100.2

As shown in Table 6, a maximum cell radius supported by LTE is 100.2 km,and at least the cell radius of the same level is required for anin-band operation using an LTE network.

The NPRACH of the NB-IoT in the related art is designed to support up to35 km of cell radius based on a GSM network. The NPRACH format supportedby the NB-IoT in the related art is shown in Table 7 below.

TABLE 7 CP duration GT duration Max. cell radius Preamble format (us)(us) (km) 0 67.5 N/A 10.1 1 266.7 N/A 40.0

As shown in Table 7, the random access preamble of the NB-IoT does notexplicitly define a guard time.

The random access procedure of the NB-IoT may support a 4-Stepcontention based RACH procedure similar to LTE in the related art asfollows.

1) MSG 1: RA preamble transmission (UE→eNB)

2) MSG 2: Receiving Random Access Response (RAR) from the eNB and RARsincluding a TA command and msg 3 scheduling (UE←eNB)

3) Msg 3: RA message including an RRC connection request and UE id(UE→eNB)

4) Msg 4: Contention resolution messages including an RRC connectionconfiguration and the UE id (UE←eNB)

Operations after Msg 4 include HARQ-ACK for msg 3, transmission of anRRC connection setup complete message including the UE id, etc.

Considering even Evolved Packet System (EPS) enhancement for the NB-IoT,the NB-IoT may support two types of following random access procedures.

Control Plane EPS Optimization

1) Msg 1: Transmitting the RA preamble

2) Msg 2: Receiving the Random Access Response (RAR) from the eNB andthe RARs including the TA command and the msg 3 scheduling

3) Msg 3: Transmitting and receiving the RRC connection request

4) Msg 4: RRC connection configuration

5) Msg 5: RRC connection setup complete (including an NAS PDU for data)

User Plane EPS Optimization

1) Msg 1: Transmitting the RA preamble

2) Msg 2: Receiving the Random Access Response (RAR) from the eNB andthe RARs including the TA command and the msg 3 scheduling

3) Msg 3: Transmitting and receiving the RRC connection request

4) Msg 4: Resuming the RRC connection

5) Msg 5: Completing the resuming of the RRC connection

6) Transmission of (N)PUSCH(UL date)

From the viewpoint of UL data transmission, first UL data transmissionis possible in msg 5 in the case of the control plane EPS optimizationand the first UL data transmission is possible after msg 5 in the caseof the user plane EPS optimization.

Since the existing NB-IoT is designed based on a GERAN networksupporting a cell radius of 35 km, the cyclic prefix (CP) of the randomaccess preamble is designed to support only up to approximately amaximum of 40 km. However, considering the in-band operation in the LTEnetwork, which is one of representative deployment scenarios of theNB-IoT, it is necessary to support a maximum cell radius of 100 kmsupported by the LTE network.

It is also necessary to support a large cell radius, even consideringthat an NB-IoT user case includes use in a location where the LTEnetwork where is not well equipped.

In order to support cell radius extension, the CP needs to be extended.For example, in order to support a cell radius of 100 km, a CP having alength covering a round trip time should be used, and a minimum lengthof the required CP is calculated by Equation 3 below.

CP length (us)=200 km/(3E8 m/s)=666.7 us  [Equation 3]

In order to support such a large cell radius, the extended CP is calledan extended CP (E-CP). Additionally, considering the delay spread, thelength of the E-CP may be designed to have a slight margin. Further, inorder to avoid overlapping of the random access preamble received fromthe UE from the viewpoint of the eNB with an immediately next adjacentsubframe, a guard time (GT) of a length (666.7 us) like the E-CP betweena frame and a next subframe capable of performing uplink transmission isrequired.

It is necessary for the eNB to individually control the uplinktransmission timing of each UE for uplink orthogonal transmission andreception. Such a process is referred to as a timing advance (TA) and aninitial timing advance is performed through the random access procedure.

In the NB-IoT, when the UE transmits the random access preamble, the eNBestimates the uplink transmission delay from the received preamble andencapsulates the estimated uplink transmission delay in the randomaccess response (RAR) message in the form of a timing advance commandand transmits the RAR message to the UE. The UE may adjust uplinktransmission timing through the TA command delivered through the RARmessage.

The random access preamble of the NB-IoT is a single carrier frequencyhopping scheme and is designed by considering both a timing estimationacquisition range and accuracy. The subcarrier spacing of the randomaccess preamble in the related art is designed to enable timingestimation without ambiguity up to a cell radius of 40 km at 3.75 kHz.

When the timing estimation is intended to be performed using a spacingbetween two subcarriers, the cell radius supportable without theambiguity may be calculated as follows. When being estimated using thespacing between two separated subcarriers, a difference between twophases is 2*pi*delta_f. Here, delta_f represents the spacing between twosubcarriers in Hz.

In order for a phase value to have a one-to-one correspondence with thecell radius, a relationship of 2*pi*delta_f*tau_RTT<2*pi needs to beestablished, and as a result, a relationship of tau_RTT<1/delta_f needsto be established for estimation without the ambiguity and a roundtripdistance is tau_RTT*(3E8 m/s). Therefore, the cell radius is1/delta_f*3E8/2=1/3.75 kHz*3E8 (m/s)/2=40 km.

Since a cell radius capable of performing the timing estimation withoutthe ambiguity is 40 km at 3.75 kHz subcarrier spacing of the randomaccess preamble in the related art, the subcarrier spacing needs to bereduced to 1.5 kHz or less in order to support a cell radius of 100 km.

As described above, a preamble newly proposed to support the 100 km cellradius may be referred to as an enhanced preamble or an enhanced NPRACHin the present invention. In contrast, the random access preamble in therelated art may be referred to as a legacy preamble or legacy NPRACH.

FIGS. 6 and 7 are diagrams illustrating an example of a hopping intervalof a preamble in a wireless communication system to which a methodproposed in this specification may be applied.

FIG. 6 illustrates a frequency hopping interval of the legacy preambleand as illustrated in FIG. 6, in the case of the legacy preamble,frequency hopping is performed with an integer multiple of a subcarrierof 3.75 kHz.

The value of the subcarrier spacing of the enhanced preamble may be 1/Ntimes (N is a positive integer) of 3.75 kHz in consideration of delayspread, interference that may occur when performing FDM with the legacypreamble, and the like. For example, when N is ‘3’, the subcarrierspacing of the enhanced preamble becomes 1.25 kHz which is ⅓ of 3.75 kHzand the cell radius may be supported up to 120 km.

Hereinafter, an enhanced preamble format may be referred to as format 2and a legacy preamble format may be referred to as format 0 or format 1.

Table 8 below shows an example of a subcarrier spacing (Δf_(RA))depending on the preamble format.

TABLE 8 Δf_(RA) Preamble format Frame Structure Type 1 Frame StructureType 2 0, 1 3.75 kHz 0-a, 1-a 3.75 kHz 2 1.25 kHz 3.75 kHz

FIG. 7 illustrates the subcarrier spacing of the enhanced preamble and aminimum frequency hopping interval compared to legacy 3.75 kHz(indicated by a dotted line).

In addition, a method for reducing the subcarrier spacing of the NPRACHmay support a larger number of preambles in the same bandwidth than thelegacy preamble through FDM. However, due to an increase in symbolduration, a preamble duration may be increased.

In terms of the time estimation, since as a minimum frequency hoppingdistance is reduced, a timing acquisition range is increased while aresidual error is increased after acquisition, a failure probabilitycompared to the legacy preamble may be increased assuming the samemaximum frequency hopping distance as the legacy preamble.

Hereinafter, an enhanced NPRACH structure will be described.

FIGS. 8A and 8B illustrate an example of a symbol group for a randomaccess in a wireless communication system to which a method proposed inthis specification may be applied.

FIG. 8A illustrates an example of the symbol group of the legacypreamble and FIG. 8B illustrates an example of the symbol group of theenhanced preamble.

The enhanced preamble may be designed to satisfy the followingrequirements by considering a problem due to a change in subcarrierspacing of the enhanced preamble and sharing or overlapping of atime/frequency resource with the legacy preamble.

i) The number of symbols constituting the symbol group may be reduced tolimit an excessive increase of the preamble duration. For example, inorder to limit the excessive increase of the preamble duration, thesymbol group may be limited to be constituted by one CP and threesymbols as illustrated in FIG. 8B. That is, the symbol group may beconstituted by a total of four symbol durations (in the case of thelegacy preamble, the symbol group is constituted by one CP and fivesymbols (a total of six symbols durations) as illustrated in FIG. 8A).

ii) An intermediate frequency hopping distance may be included in thepreamble in order to preserve performance in the time estimation. Forexample, assuming 1.25 kHz subcarrier spacing (N=3), the minimum hoppingdistance may be 1.25 kHz and the maximum hopping distance may be 1.25*18kHz (=3.75*6 kHz) to maintain similar accuracy to the legacy preamble,and the intermediate frequency hopping distance may be 1.25*3 kHz or1.25*6 kHz.

iii) The same NPRACH bandwidth as the legacy preamble may be maintained(45 kHz) to limit the sharing or overlapping of the time/frequencyresource with the legacy preamble or implementation complexity. Assumingthe 1.25 kHz subcarrier spacing (N=3), it is possible to allocate theenhanced NPRACH resource through up to a maximum of 36 startingsubcarrier indexes within a 45 kHz NPRACH bandwidth and each enhancedpreamble may perform frequency hopping within 36 subcarriers (45 kHzNPRACH bandwidth).

iv) Maximum enhanced NPRACH resource utilization needs to be able to beprovided within the NPRACH bandwidth (45 kHz). For example, allsubcarrier indexes within the NPRACH bandwidth need to be able to beallocated to the enhanced NPRACH resource.

As a method for satisfying the requirements, the following enhancedpreamble structure is proposed by assuming the 1.25 kHz (N=3) subcarrierspacing and the case where the symbol group is constituted by one CP andthree symbols (a total of four symbol durations).

The following preamble structure may be similarly to applied even to acase in which there is another subcarrier spacing value other than 1.25kHz (N=3) and a case in which the symbol group is different. In thefollowing proposal, k (k is an integer having a value from 0 to 35)represents an enhanced NPRACH starting subcarrier index within theNPRACH bandwidth. N_(SG) represents the number of symbol groups withinthe enhanced NPRACH.

Embodiment 1

The enhanced NPRACH structure may have the following features.

-   -   The enhanced NPRACH structure is constituted by six symbol        groups (N_(SG)=6).    -   Six symbol groups may support three (maximum, intermediate, and        minimum) frequency hopping distances. For example, three hopping        distances may be (1, 3, 18)*1.25 kHz.    -   With respect to the minimum and intermediate hopping distances,        symmetric frequency hopping may be supported for carrier        frequency offset (CFO) cancellation.    -   The symmetric frequency hopping means a case where two frequency        hopping is the same in terms of the hopping distance and        opposite in terms of the hopping direction. Two frequency        hopping providing symmetric hopping may be referred to as a        symmetric hopping pair. For example, when three frequency        hopping distances are constituted by (1, 3, 18)*1.25 kHz,        frequency hopping of ±1.25 kHz and ±1.25*3 kHz may be applied.    -   Minimum distance or separation between the symmetric hopping        pair

The distance or separation is displayed in units of the symbol group.For example, since a frequency hopping pattern is [k₀, k⁻¹±1, k⁻¹∓1,k⁻¹±3, k⁻¹∓3, (k⁻¹+18) mod 36] in Embodiment 1-1 and FIGS. 9A and 9Bbelow, the minimum hopping distance is 1 and the intermediate hoppingdistance is 1.

Embodiment 1-1

FIGS. 9A and 9B are diagrams illustrating an example of a frequencyhopping method of a random access preamble proposed in thisspecification.

Referring to FIG. 9A, the frequency hopping of the symbol group for theenhanced preamble may have the symmetric hopping pair, and the frequencyhopping may be performed in a pattern having a hopping interval largerthan the subcarrier of the previous symbol group.

For example, as illustrated in FIG. 9A, the frequency hopping pattern inthe preamble structure of Embodiment 1 may be as follows.

[k ₀ ,k ⁻¹±1,k ⁻¹∓1,k ⁻¹±3,k ⁻¹∓3,(k ⁻¹+18)mod 36]

In the above hopping pattern, k₀ (k₀ is an integer having a value from 0to 35) represents the enhanced NPRACH starting subcarrier index withinthe NPRACH bandwidth and k⁻¹ represents the subcarrier index of theprevious symbol group.

According to the above mapping pattern, the location to be hoppedaccording to the subcarrier index of the previous symbol group may berelatively determined from the second symbol group. That is, thelocation of the subcarrier to which the symbol group for transmission ofthe preamble is mapped may be determined to be different by a specificsubcarrier index based on the subcarrier location to which the previoussymbol group is mapped.

N_(SG) elements in square brackets indicate the subcarrier index of eachsymbol group. Hereinafter, in the present invention, frequency hoppingpatterns of N_(SG) symbol groups constituting the enhanced preamble bythe above notation are displayed.

M the above mapping pattern, ‘±’ means that the corresponding symbolgroup for transmission of the enhanced preamble may be hopped in a ‘+’or ‘-’ direction according to the subcarrier index of the previoussymbol group.

For example, in the above pattern, when k₀ is ‘0’, the hopping patternmay be [0, 1, 0, 3, 0, 18] and when k₀ is ‘1’, the hopping pattern maybe [1, 0, 1, 4, 1, 19].

Further, ‘±’ and ‘∓’ are represented to be distinguished from each otherand when hopping distances of two symbol groups are the same as eachother and are expressed by ‘±’ and ‘∓’, the two symbol groups may meanthe symmetric hopping pair.

That is, the subcarrier index is increased by the same value based onthe subcarrier index of the previous symbol group and the reduced symbolgroups may form the symmetric hopping pair, and an effect of the CFOcancellation may be obtained due to the symmetric hopping pair.

In Embodiment 1-1, when the value of N_(SG) is ‘6’ together with thefeature of Embodiment 1, the minimum distance or the separation betweenthe symmetric hopping pair may be smallest in the enhanced preamblestructure. For example, in the case of the hopping pattern described asan example in Embodiment 1-1, the minimum hopping distance and theintermediate hopping distance are ‘1’.

Embodiment 1-2

The frequency hopping of the symbol group for the enhanced preamble maybe performed in a pattern in which the index value is increased ordecreased by a specific value based on the subcarrier index of theprevious symbol group.

For example, as illustrated in FIG. 9B, the hopping pattern for thesubcarrier of the symbol group transmitting the enhanced preamble forthe NPRACH may be as follows.

[k ₀ ,k ⁻¹±1,(k ⁻¹+18)mod 36,k ⁻¹∓1,k ⁻¹±3,k ⁻¹∓3]

In Embodiment 1-2, which is the same mapping pattern as the mappingpattern illustrated in FIG. 9B, the accuracy may be enhanced becauseerror measurement of the symmetric hopping pair of the minimum hoppingdistance is more independent as compared with Embodiment 1-1 togetherwith the feature of Embodiment 1, but there may be a disadvantage interms of the minimum distance or the symmetric hopping pair as comparedwith Embodiment 1-1 because the minimum hopping distance and theintermediate hopping distances are 2 and 2, respectively.

Embodiment 2

The enhanced NPRACH structure may have the following features.

-   -   The enhanced NPRACH structure is constituted by seven symbol        groups (N_(SG)=7).    -   Seven symbol groups may support three (maximum, intermediate,        and minimum) frequency hopping distances. For example, three        hopping distances may be (1, 3, 18)*1.25 kHz.    -   With respect to the minimum and intermediate hopping distances,        symmetric frequency hopping may be supported for carrier        frequency offset (CFO) cancellation.    -   The symmetric frequency hopping means a case where two frequency        hopping is the same in terms of the hopping distance and        opposite in terms of the hopping direction. Two frequency        hopping providing symmetric hopping may be referred to as a        symmetric hopping pair. For example, when three frequency        hopping distances are constituted by (1, 3, 18)*1.25 kHz,        frequency hopping of ±1.25 kHz and ±1.25*3 kHz may be applied.    -   Minimum distance or separation between the symmetric hopping        pair

Embodiment 2-1

FIG. 10 is a diagram illustrating yet another example of a frequencyhopping method of a random access preamble proposed in thisspecification.

Referring to FIG. 10, the frequency hopping of the symbol group for theenhanced preamble may have the symmetric hopping pair, and the frequencyhopping may be performed in a pattern having a hopping interval largerthan the subcarrier of the previous symbol group. In this case, hoppingpatterns for more symbols groups than Embodiment 1-1 or 1-2 may beadded.

For example, as illustrated in FIG. 10, the frequency hopping pattern inthe preamble structure of Embodiment 2-1 may be as follows.

[k ₀ ,k ⁻¹±1,k ⁻¹∓1,k ⁻¹±3,k ⁻¹∓3,k ⁻¹±18,k ⁻¹∓18]

Embodiment 2-1 is a structure in which the value of N_(SG) is extendedto ‘7’ based on the structure described in Embodiment 2. The symmetrichopping pair for the CFO cancellation may be supported even in themaximum hopping distance through the added last symbol group as comparedwith Embodiments 1-1 and 1-2 in which the value of N_(SG) is ‘6’.

That is, the mapping pattern may be configured so that by setting thenumber of symbol groups for transmission of the enhanced preamble to aneven number except for the first symbol group (i.e., the total number ofsymbol groups is odd), all of the subcarriers of the remaining symbolgroups except for the subcarriers of the first symbol group form thesymmetric hopping pair.

By using such a mapping pattern, the performance may be improved at thetime of fine timing estimation using the maximum hopping distance.

In addition, the minimum hopping distance, the intermediate hoppingdistance, and the maximum hopping distance which are all 1 and are thuseffective in terms of the minimum distance or the separation between thesymmetric hopping pair similarly to Embodiment 1-1.

Embodiment 3

The enhanced NPRACH structure may have the following features.

-   -   The enhanced NPRACH structure is constituted by eight symbol        groups (N_(SG)=8).    -   Eight symbol groups may support three (maximum, intermediate,        and minimum) frequency hopping distances. For example, three        hopping distances may be (1, 3, 18)*1.25 kHz.    -   With respect to the minimum and intermediate hopping distances,        symmetric frequency hopping may be supported for carrier        frequency offset (CFO) cancellation.    -   The symmetric frequency hopping means a case where two frequency        hopping is the same in terms of the hopping distance and        opposite in terms of the hopping direction. Two frequency        hopping providing symmetric hopping may be referred to as a        symmetric hopping pair. For example, when three frequency        hopping distances are constituted by (1, 3, 18)*1.25 kHz,        frequency hopping of ±1.25 kHz, ±1.25*3 kHz, and ±1.25*18 kHz        may be applied.    -   Minimum distance or separation between the error measurements of        the same hopping distance

Embodiment 3-1

FIG. 11 is a diagram illustrating yet another example of a frequencyhopping method of a random access preamble proposed in thisspecification.

Referring to FIG. 11, the frequency hopping of the symbol group for theenhanced preamble may have the symmetric hopping pair, and the frequencyhopping may be performed in a pattern having a hopping interval largerthan the subcarrier of the previous symbol group. In this case, hoppingpatterns for more symbols groups than Embodiment 2-1 may be added.

For example, as illustrated in FIG. 11, the frequency hopping pattern inthe preamble structure of Embodiment 3-1 may be as follows.

[k ₀ ,k ⁻¹±1,k ⁻¹∓18,k ⁻¹±1,k ⁻¹∓18,k ⁻¹±3,k ⁻¹∓18,k ⁻¹∓3]

Since the embodiment 2-1 has a duration corresponding to four times(that is, 2² times) the legacy NPRACH duration, in the case of thelegacy NPRACH resource sharing or overlapping, the time resource may beused efficiently.

For example, when the legacy NPRACH supports 128 repetitivetransmissions at CE level 2, Embodiment 3-1 shares or overlaps thelegacy NPRACH resource and sets the number of repetitive transmissionsto 32 so that the time resource may be efficiently used without waste.

Moreover, in the case of the legacy UE, whenever the NPRACH istransmitted repeatedly 64 times for synchronization with the networkand/or measurement, a time gap of 40 ms is inserted and even inEmbodiment 3-1, the UE operates similarly to the legacy UE in terms ofinsertion of the time gap and the NPRACH resource may be shared oroverlapped without influencing the legacy UE.

In the case of Embodiment 3-2, the minimum, intermediate, and maximumhopping distances are ‘2’, ‘2’, and ‘2’, respectively.

In the enhanced NPRACH structures of Embodiments 1 to 3, in order tosatisfy a requirement (Maximum enhanced NPRACH resource utilizationshould be able to be provided within the NPRACH bandwidth (45 kHz). Forexample, all subcarrier indexes within the NPRACH bandwidth should beable to be allocated to the enhanced NPRACH resource.) of iv) describedabove, the following method may be applied to each frequency hoppingdistance.

-   -   The subcarrier index of a current symbol group may be determined        according to the location of a subcarrier index (k⁻¹) of the        previous symbol group.

For frequency hopping for a hopping distance ‘J’,

in the case of k⁻¹ Mod 2*J<J, k⁻¹+J

in the case of k⁻¹ Mod 2*J≥J, k⁻¹−J

For example, when the minimum, intermediate, and maximum frequencyhopping distances are 1, 3, and 18, respectively, the subcarrier indexof the current symbol group may be determined as follows based on thelocation of the subcarrier index (k⁻¹) of the previous symbol group.

-   -   minimum frequency hopping (minimum hopping distance=±1)        -   in the case of k⁻¹ Mod 2=0, k⁻¹+1        -   in the case of k⁻¹ Mod 2=1, k⁻¹−1    -   intermediate frequency hopping (intermediate hopping        distance=±3)        -   in the case of k⁻¹ Mod 6<3, k⁻¹+3        -   in the case of k⁻¹ Mod 6≥3, k⁻¹−3    -   maximum frequency hopping (maximum hopping distance=±3)        -   in the case of k⁻¹<18, k⁻¹+18        -   in the case of k⁻¹≥18, k⁻¹−18

That is, by comparing the value of the subcarrier index of the previoussymbol group with a specific value, the subcarrier index of the symbolgroup for the frequency hopping may be determined.

Embodiments 1-1 and 1-2 do not support the symmetric frequency hoppingfor the maximum frequency hopping distance (1.25*18 kHz) due to thelimitation of the number of symbol groups in the preamble.

That is, since the number of symbol groups is limited only to a maximumof 6, the subcarriers of the symbol group are not symmetric at themaximum hopping distance.

FIGS. 12A and 12B are diagrams illustrating still yet another example ofa frequency hopping method of a random access preamble proposed in thisspecification.

Referring to FIGS. 12A and 12B, when the symmetric frequency hopping isnot supported at the maximum hopping distance, the symmetric hoppingpair may be formed in an entire duration in which the preamble istransmitted, by supporting the symmetric frequency hopping betweenrepeated transmissions of preambles.

For the maximum hopping distance for the fine timing estimation, thesymmetric hopping pair may be supported between repeated transmissionsof the enhanced preamble in order to enhance the performance through theCFO cancellation by the following method.

-   -   If the preamble repetition number is Rmax and the preamble        repetition index is r (r=0, 1, 2, . . . , Rmax−1),        -   when r mode 2 is ‘0’, the enhanced preamble may be generated            through the method of Embodiment 1. In this case, if r>0, a            starting subcarrier index of every repetition of the            enhanced preamble may be generated (pseudo)randomly for            inter-cell interference randomization.        -   when r mode 2 is ‘1’, the mapping pattern such as the            symmetric hopping pair may be formed by using the enhanced            preamble generated a previous repetition index (r−1) and the            following method.    -   The mapping pattern such as the symmetric hopping pair may be        configured by mirroring the hopping pattern of the enhanced        preamble generated in the previous repetition index (r−1) on a        time reversal or time axis or configuring the hopping pattern of        the enhanced preamble to be symmetric on the time axis.    -   In this case, the starting subcarrier index is equal to a last        subcarrier index of the symbol group in the previous repetition        index (r−1) as illustrated in FIG. 12A or the starting        subcarrier index is generated (or configured) (pseudo-)randomly        in order to additionally perform the inter-cell interference        randomization and the location of the starting subcarrier index        may be limited.

For example, as illustrated in FIG. 12B, in Embodiment 1-1, when thesubcarrier index of the last symbol group of the previous repetitionindex (r−1) is smaller than 18 so that the symmetric hopping pairbetween the subcarriers is formed for the maximum hopping distance, thestarting subcarrier index may be (pseudo)randomly selected among valuessmaller than 18 and when the subcarrier index of the last symbol groupin the previous repetition index (r−1) is equal to or larger than 18,the starting subcarrier index may be (pseudo)randomly selected amongvalues among values equal to or larger than 18.

That is, when the maximum number of symbol groups is an even number, thesymmetric hopping pair between the subcarriers is not formed at themaximum hopping distance. Therefore, the subcarrier index of the symbolgroup may be configured so as to have the symmetric frequency hoppingform between repeated transmissions by using repeated transmissioncharacteristics of the enhanced preamble.

Even when the symmetric hopping pair is not formed at the maximumhopping distance according to the number of symbol groups by using sucha method, the symmetric frequency hopping pair between repeatedtransmissions may be formed and the CFO cancellation may be performed.

Embodiment 5

FIG. 13 is a diagram illustrating an example of a time gap configuringmethod of a random access preamble proposed in this specification.

Referring to FIG. 13, when the enhanced preamble or an improved NPRACHor the enhanced NPRACH is repeatedly transmitted, the time gap isinserted in the middle of the repeated transmission, thereby preventingsynchronization between the UE and the eNB from varying due to repeatedtransmission.

Specifically, when the UE repeatedly transmits the enhanced NPRACH for along period of time, it may occur that the uplink transmission isstopped in the middle and a downlink signal is received from the networkin order to periodically synchronize with the network.

In order to provide a synchronization period as in the legacy UE, theenhanced NPRACH may be transmitted during an ‘X’ duration from atransmission start time of the enhanced NPRACH and uplink transmissionmay be delayed or punctured during a ‘Y’ duration.

Delaying in the present invention may mean that uplink transmission datais held during the ‘Y’ duration and enhanced NPRACH transmission isresumed in succession to data which is previously transmitted again at atime after the ‘Y’ duration.

Further, puncturing in the present invention may mean that datagenerated during the ‘Y’ duration is skipped or discarded from a starttime when the uplink transmission is stopped and transmission is resumedfrom the enhanced NPRACH after the data is skipped or discarded duringthe ‘Y’ duration.

That is, in the case of the enhanced preamble, since the length and thestructure of the symbol for preamble transmission vary as describedabove, the gap may be inserted in the middle of the repeatedtransmission of the enhanced preamble in order to prevent thesynchronization from being changed by repeatedly transmitting theenhanced preamble over a long interval.

In other words, when the length and the structure of the symbol fortransmission of the enhanced preamble are configured differently fromthe length and the structure of the symbol for transmission of thelegacy preamble, and the enhanced preamble is repeatedly transmitted fora long time, the UE and the eNB may synchronize with each other.

Therefore, it is necessary to prevent the UE and the eNB fromsynchronizing with each other by inserting the gap in the middle of therepeated transmission of the enhanced preamble.

In this case, since the uplink transmission is not performed in theinserted gap duration, data generated during the gap duration may beskipped or transmission of uplink data may be held and transmission ofthe enhanced preamble may be performed again from a duration after thegap.

The time when the enhanced NPRACH transmission is performed again may bea time when the ‘Y’ duration ends or limited to a 1 ms unit or aboundary of the subframe. In this case, in the latter case, the uplinktransmission may be delayed during the ‘Y’ duration or the enhancedNPRACH transmission may be resumed in the first 1 ms unit (or subframeboundary) after puncturing.

In this case, a value of ‘X’ for inserting the gap duration may be setthrough two methods described below.

(Method 1)

The duration ‘X’ for inserting the gap for repeated transmission of theenhanced preamble may be determined based on the repeated transmissionperiod of the legacy preamble.

Specifically, the subcarrier spacing of the enhanced preamble is reducedby one-third times compared to the subcarrier spacing of the legacypreamble and the symbol interval is increased by three times. Therefore,although the symbol durations of the legacy preamble and the enhancedpreamble do not clearly coincide with each other, an enhanced preamblegap setting period ‘X’ may be set based on the transmission period ofthe legacy preamble in order to maintain compatibility with the legacypreamble.

For example, the value of ‘X’ may be set as shown in Equation 4 below.

X=64*T _(P,L)  [Equation 4]

In Equation 4, T_(P,L) may denote a legacy preamble duration (ms).

In the case of Method 1, the gap setting duration ‘X’ of the enhancedpreamble may be set using the same value as the gap setting duration ‘X’in the legacy preamble.

That is, when the legacy preamble is repeatedly transmitted, the valueof ‘X’ is set based on an integer multiple of the legacy preambleduration, and as a result, when legacy NPRACH time/frequency resourcesare shared or the resources are overlapped, a collision with the legacyNPUSCH scheduled during the Y duration may be avoided.

(Method 2)

The duration ‘X’ for inserting the gap for repeated transmission of theenhanced preamble may be determined based on the repeated transmissionperiod of the enhanced preamble.

Specifically, the value of ‘X’ may be determined based on one of thevalues equal to or smaller than ‘64’, which is an integral multiple ofthe symbol duration of the enhanced NPRACH and the number of repetitionsof the legacy NPRACH.

That is, in the case of the structure (i.e., the preamble format 2)according to the enhanced preamble format, the gap setting duration ‘X’of the enhanced preamble may be set according to Equation 5 below.

X=N*T _(P,E)  [Equation 5]

In Equation 5, T_(P,E) may denote an enhanced preamble duration (ms).That is, T_(P,E) denotes a duration in which the enhanced preamble istransmitted.

‘X’ denotes a value for delaying or puncturing the uplink transmissionin units of the enhanced preamble. That is, after the enhanced preambleis repeatedly transmitted during the ‘X’ duration, the gap may beinserted.

In other words, the UE may repeatedly transmit the preamble to the eNBduring the ‘X’ duration and delay or puncture the uplink transmission asdescribed above during the gap duration or perform an operation ofsynchronization with the eNB so as to prevent the UE and the eNB frombeing synchronized with each other.

Thereafter, when the gap duration ends, the UE may repeatedly transmitthe enhanced preamble to the eNB again.

In Equation 5, N may be set to a maximum value among non-negativeintegers to satisfy the condition of Equation 6 below or a maximum valueamong repetition frequency values supported by the enhanced NPRACH.

N*T _(P,E)≤64*T _(P,L)  [Equation 6]

That is, the value of N may mean the number of times the enhancedpreamble is repeatedly transmitted and may be set to a maximum valuesatisfying Equation 5.

T_(P,L) is configured by 4(T_(CP)+T_(SEQ)) and T_(C,P) is configured by6(T_(CP)+T_(SEQ)), the value of ‘N’ may become 16 which is the largestvalue of positive numbers satisfying Equation 5 above. That is, in thecase of the legacy preamble (preamble format 0 or 1), the legacypreamble may be repeatedly transmitted a predetermined number of times(for example, 64 times) during a duration of 4*64*(T_(CP)+T_(SEQ)) andthen, the gap may be inserted and in the case of the enhanced preamble(preamble format 2), the enhanced preamble may be repeatedly transmitteda predetermined number of times (e.g., 16 times) during a duration of16*6*(T_(CP)+T_(SEQ)) and then, the gap may be inserted.

For example, assuming that 64*T_(P,L) is ‘409.6 ms’ and in the case ofthe preamble structure of Embodiment 1, the value of T_(P,E) becomes‘19.2 ms’, so that the maximum positive integer N satisfying thecondition of Equation 5 becomes 21.

Alternatively, when the number of repeated transmission times of theenhanced preamble supports only 2{circumflex over ( )}M (M is anon-negative integer), that is, when the number of repeated transmissiontimes supports only values of {1, 2, 4, 8, 16, 32}, N may become 16.

In this case, the UE may repeatedly transmit the enhanced preamble ofpreamble format 2 to the eNB based on configuration transmitted from theeNB a predetermined number of times during the set ‘X’ duration andthen, may synchronize with the eNB without transmitting the enhancedpreamble during the inserted gap duration.

Thereafter, when the gap duration ends, the UE may repeatedly transmitthe enhanced preamble to the eNB again.

The ‘X’ value for the enhanced NPRACH may be a value scaled according tothe T_(P,L) which varies depending on the format of the legacy preambleand may adopt a value of T_(P,L,min) instead of T_(P,L) in the ‘X’ valuedetermining method in order to use a fixed ‘X’ value regardless of thelegacy preamble format.

Here, T_(P,L,min) denotes a minimum values among values depending on thelegacy preamble format.

The value ‘Y’ of the inserted gap may be set as follows.

(Method 1)

Similar to method 1 for obtaining the value of ‘X’ above, since the samesynchronization time as the legacy NPRACH transmission may be required,the ‘X’ value may be set to 40 ms which is similar to the preambletransmission gap setting duration of the legacy UE.

In this case, the value of ‘X’ may be set through Method 1 or 2described above.

That is, for compatibility with legacy UEs, the value of ‘Y’ may be setto the same value as that of the legacy UE.

In this case, since the ‘Y’ value has the same value as that of thelegacy UE, the compatibility with the legacy UE is maintained.

(Method 2)

The inserted gap duration may be set to a minimum value (for example,91.2 ms) of consecutive durations including all gap durations accordingto the legacy preamble format (preamble format 0 and/or 1).

In the preamble format 2, the ‘Y’ value may be set to the minimum valueof consecutive durations so as to include all of ‘Y’ assuming preambleformats 0 and 1.

That is, the ‘Y’ value of the enhanced NPRACH may be set to the minimumvalue of the consecutive durations including both a ‘Y1’ value in legacypreamble format ‘0’ and a ‘Y2’ value in preamble format ‘1’.

For example, if ‘Y1’ is 40 ms and the value of ‘Y2’ is 40, the value of‘Y’ may be set to 91.2 ms.

The transmission resumption time of the enhanced NPRACH may be the timewhen the Y duration ends (the same time as the legacy NPRACH) or may belimited to the first 1 ms unit or subframe boundary after the end of theY duration. Alternatively, the enhanced NPRACH repetition may again beresumed at the boundary of the enhanced NPRACH repetition, assumingthere is no Y duration.

By using such a method, the number of repeated transmission times andthe value of the inserted gap may be determined in consideration of thecompatibility with the legacy UE and the resource utilizationefficiency.

FIG. 14 is a flowchart illustrating an example of an operation method ofa UE that performs a method proposed in this specification.

First, the UE may receive the configuration information from the eNB inorder to transmit the enhanced preamble and receive downlink controlinformation (DCI) through the configuration information.

In this case, the DCI may include resource information (e.g., asubcarrier index, etc.) for transmission of the enhanced preamble by theUE.

Thereafter, the UE transmits to the eNB a random access preamble(enhanced NPRACH or enhanced preamble) according to a specific preamblestructure in the subcarrier allocated by the eNB (S14010).

In this case, the specific preamble structure may have the structuresdescribed in Embodiments 1 and 2 and may be configured similar toPreamble format 2.

For example, the specific preamble structure may be constituted by oneCP and three symbols and a subcarrier gap may be set to 1.25 kHz.

Thereafter, the UE receives, from the eNB, a random access responsemessage in response to the random access preamble (S14020).

The random access response message may include a TA command and supportinformation for matching timing synchronization between the UE and theeNB as described above and the UE may perform uplink transmission afteradjusting the timing by performing synchronization with the eNB based onthe TA command.

The random access preamble may be repeatedly transmitted 16 times duringa predetermined duration and the gap may be inserted for a predeterminedtime and the predetermined duration may be determined by multiplying atransmission duration in which the random access preamble is transmittedby the number of repeated transmission times.

That is, as described in Embodiment 5, in the case of the random accesspreamble, the number of repeated transmission times in which the gap isconfigured may be set to a specific (for example, 16) and the insertedgap may be set a value (e.g., 40 ms) for compatibility with the legacyUE or a value (e.g., 91.2 ms) including all gap values of the preambleformats of the legacy preamble.

In this case, the number of repeated transmission times may be setthrough the method described in Method 1 or 2 of Embodiment 5.

For example, the number of repeated transmission times may be set to aninteger multiple of the symbol duration of the enhanced preamble and toa largest value among values of non-negative integers smaller than thenumber of repeated transmission times of the legacy preamble.

In this regard, the operation of the UE described above may bespecifically implemented by UE devices 1620 and 1720 illustrated inFIGS. 16 and 17 of this specification. For example, the operation of theUE described above may be performed by processors 1621 and 1721 and/orRF units (or modules) 1623 and 1725.

Specifically, the processors 1621 and 1721 may control to receive theconfiguration information from the eNB in order to transmit the enhancedpreamble through the RF units (or modules) 1623 and 1725 and receive thedownlink control information (DCI) through the configurationinformation.

In this case, the DCI may include resource information (e.g., asubcarrier index, etc.) for transmission of the enhanced preamble by theUE.

Thereafter, the processors 1621 and 1721 may control to transmit to theeNB the random access preamble (enhanced NPRACH or enhanced preamble)according to a specific preamble structure in subcarriers allocated bythe eNB through the RF units (or modules) 1623 and 1725.

In this case, the specific preamble structure may have the structuresdescribed in Embodiments 1 and 2 and may be configured similar topreamble format 2.

For example, the specific preamble structure may be constituted by oneCP and three symbols and a subcarrier gap may be set to 1.25 kHz.

Thereafter, the processors 1621 and 1721 may control to receive from theeNB the random access response message in response to the random accesspreamble through the RF units (or modules) 1623 and 1725.

The random access response message may include a TA command and supportinformation for matching timing synchronization between the UE and theeNB as described above and the UE may perform uplink transmission afteradjusting the timing by performing synchronization with the eNB based onthe TA command.

The random access preamble may be repeatedly transmitted 16 times duringa predetermined duration and the gap may be inserted for a predeterminedtime and the predetermined duration may be determined by multiplying atransmission duration in which the random access preamble is transmittedby the number of repeated transmission times.

That is, as described in Embodiment 5, in the case of the random accesspreamble, the number of repeated transmission times in which the gap isconfigured may be set to a specific (for example, 16) and the insertedgap may be set a value (e.g., 40 ms) for compatibility with the legacyUE or a value (e.g., 91.2 ms) including all gap values of the preambleformats of the legacy preamble.

In this case, the number of repeated transmission times may be setthrough the method described in Method 1 or 2 of Embodiment 5.

For example, the number of repeated transmission times may be set to aninteger multiple of the symbol duration of the enhanced preamble and toa largest value among values of non-negative integers smaller than thenumber of repeated transmission times of the legacy preamble.

FIG. 15 is a flowchart illustrating an example of an operation method ofan eNB that performs a method proposed in this specification.

First, the eNB may transmit to the UE the configuration information inorder to transmit the enhanced preamble and transmit the downlinkcontrol information (DCI) through the configuration information.

In this case, the DCI may include resource information (e.g., asubcarrier index, etc.) for transmission of the enhanced preamble by theUE.

Thereafter, the eNB receives from the eNB the random access preamble(enhanced NPRACH or enhanced preamble) according to the specificpreamble structure in the subcarrier allocated to the UE (S15010).

In this case, the specific preamble structure may have the structuresdescribed in Embodiments 1 and 2 and may be configured similar topreamble format 2.

For example, the specific preamble structure may be constituted by oneCP and three symbols and a subcarrier gap may be set to 1.25 kHz.

Thereafter, the eNB transmits, to the UE, the random access responsemessage in response to the random access preamble (S15020).

The random access response message may include a TA command and supportinformation for matching timing synchronization between the UE and theeNB as described above and the UE may perform uplink transmission afteradjusting the timing by performing synchronization with the eNB based onthe TA command.

The random access preamble may be repeatedly transmitted 16 times duringa predetermined duration and the gap may be inserted for a predeterminedtime and the predetermined duration may be determined by multiplying atransmission duration in which the random access preamble is transmittedby the number of repeated transmission times.

That is, as described in Embodiment 5, in the case of the random accesspreamble, the number of repeated transmission times in which the gap isconfigured may be set to a specific (for example, 16) and the insertedgap may be set a value (e.g., 40 ms) for compatibility with the legacyUE or a value (e.g., 91.2 ms) including all gap values of the preambleformats of the legacy preamble.

In this case, the number of repeated transmission times may be setthrough the method described in Method 1 or 2 of Embodiment 5.

For example, the number of repeated transmission times may be set to aninteger multiple of the symbol duration of the enhanced preamble and toa largest value among values of non-negative integers smaller than thenumber of repeated transmission times of the legacy preamble.

In this regard, the operation of the eNB described above may bespecifically implemented by eNB devices 1610 and 1710 illustrated inFIGS. 16 and 17 of this specification. For example, the operation of theeNB described above may be performed by the processors 1611 and 1711and/or RF units (or modules) 1613 and 1715.

Specifically, the processors 1611 and 1711 may control to receive theconfiguration information from the eNB in order to transmit the enhancedpreamble through the RF units (or modules) 1613 and 1715 and receive thedownlink control information (DCI) through the configurationinformation.

In this case, the DCI may include resource information (e.g., asubcarrier index, etc.) for transmission of the enhanced preamble by theUE.

Thereafter, the processors 1611 and 1711 may control to receive from theUE the random access preamble (enhanced NPRACH or enhanced preamble)according to the specific preamble structure in subcarriers allocated tothe UE through the RF units (or modules) 1613 and 1715.

In this case, the specific preamble structure may have the structuresdescribed in Embodiments 1 and 2 and may be configured similar topreamble format 2.

For example, the specific preamble structure may be constituted by oneCP and three symbols and a subcarrier gap may be set to 1.25 kHz.

Thereafter, the processors 1611 and 1711 may control to transmit to theUE the random access response message in response to the random accesspreamble through the RF units (or modules) 1613 and 1715.

The random access response message may include a TA command and supportinformation for matching timing synchronization between the UE and theeNB as described above and the UE may perform uplink transmission afteradjusting the timing by performing synchronization with the eNB based onthe TA command.

The random access preamble may be repeatedly transmitted 16 times duringa predetermined duration and the gap may be inserted for a predeterminedtime and the predetermined duration may be determined by multiplying atransmission duration in which the random access preamble is transmittedby the number of repeated transmission times.

That is, as described in Embodiment 5, in the case of the random accesspreamble, the number of repeated transmission times in which the gap isconfigured may be set to a specific (for example, 16) and the insertedgap may be set a value (e.g., 40 ms) for compatibility with the legacyUE or a value (e.g., 91.2 ms) including all gap values of the preambleformats of the legacy preamble.

In this case, the number of repeated transmission times may be setthrough the method described in Method 1 or 2 of Embodiment 5.

For example, the number of repeated transmission times may be set to aninteger multiple of the symbol duration of the enhanced preamble and toa largest value among values of non-negative integers smaller than thenumber of repeated transmission times of the legacy preamble.

Overview of Devices to which Present Invention is Applicable

FIG. 16 illustrates a block diagram of a wireless communication deviceto which methods proposed in this specification may be applied.

Referring to FIG. 16, a wireless communication system includes an eNB1610 and multiple user equipments 1620 positioned within an area of theeNB.

Each of the eNB and the UE may be expressed as a wireless device.

In this case, the eNB 1610 and the UE 1620 may be referred to as a firstdevice or a second device.

The first device may be the eNB, a network node, a transmittingterminal, a receiving terminal, a wireless device, a wirelesscommunication device, a vehicle, a vehicle equipped with an autonomousdriving function, a connected car, a unmanned aerial vehicle, UAV), anArtificial Intelligence (AI) module, a robot, an Augmented Reality (AR)device, a Virtual Reality (VR) device, a Mixed Reality (MR) device, ahologram device, a public safety device, an MTC device, an IoT device, amedical device, a pin-tec device (or financial device), a securitydevice, a climate/environmental device, devices related to 5G services,or other devices related to fourth industrial revolution fields.

The second device may be the eNB, a network node, a transmittingterminal, a receiving terminal, a wireless device, a wirelesscommunication device, a vehicle, a vehicle equipped with an autonomousdriving function, a connected car, a unmanned aerial vehicle, UAV), anArtificial Intelligence (AI) module, a robot, an Augmented Reality (AR)device, a Virtual Reality (VR) device, a Mixed Reality (MR) device, ahologram device, a public safety device, an MTC device, an IoT device, amedical device, a pin-tec device (or financial device), a securitydevice, a climate/environmental device, devices related to 5G services,or other devices related to fourth industrial revolution fields.

For example, the UE may include a cellular phone, a smart phone, alaptop computer, a digital broadcasting terminal, a personal digitalassistants (PDA), a portable multimedia player (PMP), a navigation, aslate PC, a tablet PC, an ultrabook, a wearable device such as asmartwatch, a smart glass, or a head mounted display (HMD)), etc. Forexample, the HMD may be a display device worn on a head. For example, anHMD may be used to implement the VR, AR, or MR.

For example, the UAV may be a flying object that is not ridden by peoplebut that flies by radio control signals. For example, the VR device mayinclude a device that implements an object or background in a virtualworld. For example, the AR device may include a device that connects andimplements the object or background in the real world to the object orbackground in a real world. For example, the MR device may include adevice that fuses and implements the object or background in the virtualworld with the object or background in the real world. For example, thehologram device may include a device for implementing a 360-degreestereoscopic image by recording and reproducing stereoscopic informationby utilizing a phenomenon of interference of light generated by the twolaser lights meeting with each other, called holography. For example,the public safety device may include a video relay device or a videodevice that may be worn by a body of a user. For example, the MTC deviceand the IoT device may be a device which does not require direct humanintervention or manipulation. For example, the MTC device and the IoTdevice may include a smart meter, a vending machine, a thermometer, asmart bulb, a door lock, or various sensors. For example, the medicaldevice may be a device used for diagnosing, treating, alleviating,treating, or preventing a disease. For example, the medical device maybe a device used for diagnosing, treating, alleviating, or correcting aninjury or disability. For example, the medical device may be a deviceused for inspecting, replacing, or modifying a structure or function.For example, the medical device may be a device used for controllingpregnancy. For example, the medical device may include a medicaltreatment device, a surgical device, an (in vitro) diagnostic device, ahearing aid or a (medical) procedure device, and the like. For example,the security device may be a device installed to prevent a risk that mayoccur and to maintain safety. For example, the security device may be acamera, a CCTV, a recorder, or a black box. For example, the pin-tecdevice may be a device capable of providing financial services such asmobile payment. For example, the pin-tec device may include a paymentdevice or a point of sales (POS). For example, the climate/environmentaldevice may include a device for monitoring or predicting aclimate/environment.

The eNB 1610 includes a processor 1611, a memory 1612, and a radiofrequency (RF) module 1613. The processor 1611 implements a function, aprocess, and/or a method which are proposed in FIGS. 1 to 15 andEmbodiments 1 to 5 above. Layers of a radio interface protocol may beimplemented by the processor. The memory is connected with the processorto store various information for driving the processor. The RF module isconnected with the processor to transmit and/or receive a radio signal.

The UE includes a processor 1621, a memory 1622, and an RF module 1623.

The processor implements a function, a process, and/or a method whichare proposed in FIGS. 1 to 15 and Embodiments 1 to 5 above. Layers of aradio interface protocol may be implemented by the processor. The memoryis connected with the processor to store various information for drivingthe processor. The RF module 1623 is connected with the processor totransmit and/or receive a radio signal.

The memories 1612 and 1622 may be positioned inside or outside theprocessors 1611 and 1621 and connected with the processor by variouswell-known means.

Further, the eNB and/or the UE may have a single antenna or multipleantennas.

FIG. 17 illustrates another example of the block diagram of the wirelesscommunication device to which the methods proposed in this specificationmay be applied.

Referring to FIG. 17, a wireless communication system includes a basestation 1710 and multiple user equipments 1720 positioned within an areaof the base station. The eNB may be represented by a transmittingapparatus and the UE may be represented by a receiving apparatus, orvice versa. The eNB and the UE include processors 1711.1721 and1714.1724, memories 1715.1725 and 1712.1722, one or more Tx/Rx radiofrequency (RF) modules 1713.1723 and 1716.1726, Tx processors 2112 and2122, Rx processors 2113 and 2123, and antennas 2116 and 2126. Theprocessor implements a function, a process, and/or a method which aredescribed above. More specifically, a higher layer packet from a corenetwork is provided to the processor 1711 in DL (communication from theeNB to the UE). The processor implements a function of an L2 layer. Inthe DL, the processor provides multiplexing between a logical channeland a transmission channel and allocation of radio resources to the UE1720, and takes charge of signaling to the UE. The transmit (TX)processor 1712 implement various signal processing functions for an L1layer (i.e., physical layer). The signal processing functions facilitateforward error correction (FEC) at the UE and include coding andinterleaving. Encoded and modulated symbols are divided into parallelstreams, each stream is mapped to an OFDM subcarrier, multiplexed with areference signal (RS) in a time and/or frequency domain, and combinedtogether by using inverse fast Fourier transform (IFFT) to create aphysical channel carrying a time domain OFDMA symbol stream. An OFDMstream is spatially precoded in order to create multiple spatialstreams. Respective spatial streams may be provided to differentantennas 1716 via individual Tx/Rx modules (or transceivers, 1715). EachTx/Rx module may modulate an RF carrier into each spatial stream fortransmission. In the UE, each Tx/Rx module (or transceiver, 1726)receives a signal through each antenna 1726 of each Tx/Rx module. EachTx/Rx module reconstructs information modulated with the RF carrier andprovides the reconstructed information to the receive (RX) processor1723. The RX processor implements various signal processing functions oflayer 1. The RX processor may perform spatial processing on informationin order to reconstruct an arbitrary spatial stream which is directedfor the UE. When multiple spatial streams are directed to the UE, themultiple spatial streams may be combined into a single OFDMA symbolstream by multiple RX processors. The RX processor transforms the OFDMAsymbol stream from the time domain to the frequency domain by using fastFourier transform (FFT). A frequency domain signal includes individualOFDMA symbol streams for respective subcarriers of the OFDM signal.Symbols on the respective subcarriers and the reference signal arereconstructed and demodulated by determining most likely signalarrangement points transmitted by the base station. The soft decisionsmay be based on channel estimation values. The soft decisions aredecoded and deinterleaved to reconstruct data and control signalsoriginally transmitted by the eNB on the physical channel. Thecorresponding data and control signals are provided to the processor1721.

UL (communication from the UE to the base station) is processed by theeNB 1710 in a scheme similar to a scheme described in association with areceiver function in the UE 1720. Each Tx/Rx module 1725 receives thesignal through each antenna 1726. Each Tx/Rx module provides the RFcarrier and information to the RX processor 1723. The processor 1721 maybe associated with the memory 1724 storing a program code and data. Thememory may be referred to as a computer readable medium.

In this specification, a wireless device may be the eNB, a network node,a transmitting terminal, a receiving terminal, a wireless device, awireless communication device, a vehicle, a vehicle equipped with anautonomous driving function, a connected car, a unmanned aerial vehicle,UAV), an Artificial Intelligence (AI) module, a robot, an AugmentedReality (AR) device, a Virtual Reality (VR) device, an MTC device, anIoT device, a medical device, a pin-tec device (or financial device), asecurity device, a climate/environmental device, or other devicesrelated to fourth industrial revolution fields or 5G services. Forexample, the UAV may be a flying object that is not ridden by people butthat flies by radio control signals. For example, the MTC device and theIoT device as devices that do not require direct human intervention ormanipulation may include a smart meter, a vending machine, athermometer, a smart bulb, a door lock, or various sensors. For example,the medical device as a device used for the purpose of diagnosis,treatment, alleviation, therapy, or prevention of a disease or a deviceused for the purpose of inspecting, replacing, or modifying a structureor function may include a treatment equipment, a surgical device, an (invitro) diagnostic device, a hearing aid, a procedure device, etc. Forexample, the security device as a device installed to prevent a riskthat may occur and to maintain safety may include a camera, a CCTV, ablack box, etc. For example, the pin-tec device as a device capable ofproviding financial services such as mobile payment may include apayment device, a point of sales (POS), etc. For example, theclimate/environmental device may mean a device for monitoring orpredicting a climate/environment.

In this specification, the UE may include a cellular phone, a smartphone, a laptop computer, a digital broadcasting terminal, a personaldigital assistants (PDA), a portable multimedia player (PMP), anavigation, a slate PC, a tablet PC, an ultrabook, a wearable devicesuch as a smartwatch, a smart glass, or a head mounted display (HMD)),etc. For example, the HMD as a head-worn type display device may be usedto implement the VR or AR.

In the embodiments described above, the components and the features ofthe present invention are combined in a predetermined form. Eachcomponent or feature should be considered as an option unless otherwiseexpressly stated. Each component or feature may be implemented not to beassociated with other components or features. Further, the embodiment ofthe present invention may be configured by associating some componentsand/or features. The order of the operations described in theembodiments of the present invention may be changed. Some components orfeatures of any embodiment may be included in another embodiment orreplaced with the component and the feature corresponding to anotherembodiment. It is apparent that the claims that are not expressly citedin the claims are combined to form an embodiment or be included in a newclaim by an amendment after the application.

The embodiments of the present invention may be implemented by hardware,firmware, software, or combinations thereof. In the case ofimplementation by hardware, according to hardware implementation, theexemplary embodiment described herein may be implemented by using one ormore application specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), field programmable gate arrays(FPGAs), processors, controllers, micro-controllers, microprocessors,and the like.

In the case of implementation by firmware or software, the embodiment ofthe present invention may be implemented in the form of a module, aprocedure, a function, and the like to perform the functions oroperations described above. A software code may be stored in the memoryand executed by the processor. The memory may be positioned inside oroutside the processor and may transmit and receive data to/from theprocessor by already various means.

It is apparent to those skilled in the art that the present inventionmay be embodied in other specific forms without departing from essentialcharacteristics of the present invention. Accordingly, theaforementioned detailed description should not be construed asrestrictive in all terms and should be exemplarily considered. The scopeof the present invention should be determined by rational construing ofthe appended claims and all modifications within an equivalent scope ofthe present invention are included in the scope of the presentinvention.

What is claimed is:
 1. A method for transmitting a random accesspreamble by a user equipment (UE) in a wireless communication systemsupporting a narrow band-Internet of things (NB-IoT), the methodcomprising: transmitting, to a base station, a random access preambleaccording to a specific preamble structure in a subcarrier allocated bythe base station; and receiving, from the base station, a random accessresponse message in response to the random access preamble, wherein agap is inserted for a predetermined time after the random accesspreamble is repeatedly transmitted 16 times during a predeterminedduration, and wherein the predetermined duration is determined bymultiplying a transmission duration transmitted by the random accesspreamble by the number of repeated transmission times of the randomaccess preamble.
 2. The method of claim 1, wherein the transmissionduration is constituted by a symbol group of a Cyclic Prefix (CP) andthree symbols according to the specific preamble structure.
 3. Themethod of claim 2, wherein a subcarrier of the symbol group is hopped ona frequency axis in a specific pattern constituted by a hopping pairsymmetric according to the specific preamble structure.
 4. The method ofclaim 3, wherein subcarrier indexes of second and third symbol groupsare values larger than a subcarrier index of a previous symbol group by‘1’ or smaller than the subcarrier index by ‘1’ based on a start symbolgroup of the specific pattern, wherein subcarrier indexes of the thirdsymbol group and a fourth symbol group are values larger than thesubcarrier index by ‘3’ or smaller than the subcarrier index ‘3’, andwherein a subcarrier index of a fifth symbol group is a value largerthan the subcarrier index of the previous symbol group by ‘18’.
 5. Themethod of claim 1, wherein a subcarrier spacing is 1.25 kHz in thespecific preamble structure.
 6. The method of claim 1, wherein the gapis ‘40’ ms.
 7. The method of claim 1, wherein the random access responsemessage includes a timing advance command value for adjusting uplinktransmission timing of the UE.
 8. The method of claim 7, furthercomprising: performing uplink transmission based on the timing advancecommand value.
 9. A method for receiving a random access preamble by abase station in a wireless communication system supporting a narrowband-Internet of things (NB-IoT), the method comprising: receiving, froma UE, a random access preamble according to a specific preamblestructure in an allocated subcarrier; and transmitting, to the UE, arandom access response message in response to the random accesspreamble, wherein a gap is inserted for a predetermined time after therandom access preamble is repeatedly transmitted 16 times during apredetermined duration, and wherein the predetermined duration isdetermined by multiplying a transmission duration transmitted by therandom access preamble by the number of repeated transmission times ofthe random access preamble.
 10. A UE transmitting a random accesspreamble in a wireless communication system supporting a narrowband-Internet of things (NB-IoT), the UE comprising: a radio frequency(RF) module for transmitting and receiving a radio signal; and aprocessor functionally connected with the RF module, wherein theprocessor is configured to transmit, to a base station, a random accesspreamble according to a specific preamble structure in a subcarrierallocated by the base station, and receive, from the base station, arandom access response message in response to the random accesspreamble, and wherein a gap is inserted for a predetermined time afterthe random access preamble is repeatedly transmitted 16 times during apredetermined duration, and wherein the predetermined duration isdetermined by multiplying a transmission duration transmitted by therandom access preamble by the number of repeated transmission times ofthe random access preamble.
 11. The UE of claim 10, wherein thetransmission duration is constituted by a symbol group of a CyclicPrefix (CP) and three symbols according to the specific preamblestructure.
 12. The UE of claim 11, wherein a subcarrier of the symbolgroup is hopped on a frequency axis in a specific pattern constituted bya hopping pair symmetric according to the specific preamble structure.13. The UE of claim 12, wherein subcarrier indexes of second and thirdsymbol groups are values larger than a subcarrier index of a previoussymbol group by ‘1’ or smaller than the subcarrier index by ‘1’ based ona start symbol group of the specific pattern, wherein subcarrier indexesof the third symbol group and a fourth symbol group are values largerthan the subcarrier index by ‘3’ or smaller than the subcarrier index‘3’, and wherein a subcarrier index of a fifth symbol group is a valuelarger than the subcarrier index of the previous symbol group by ‘18’.14. The UE of claim 10, wherein a subcarrier spacing is 1.25 kHz in thespecific preamble structure.
 15. The UE of claim 10, wherein the gap is‘40’ ms.
 16. The UE of claim 10, wherein the random access responsemessage includes a timing advance command value for adjusting uplinktransmission timing of the UE.
 17. The UE of claim 16, wherein theprocessor performs uplink transmission based on the timing advancecommand value.